The idea that poor people do not get top notch medical care in the US is largely a myth. It might not be quite as nice but it is often nearly as effective. A large part of the reason medical care is so expensive for average people is that they are subsidizing the healthcare of poor people. This is why the average survival rates for most cancers are higher in the US than anywhere else in the world; people that cannot afford it still get treated with the state of the art and the cost is passed on to people with insurance.
A poor person with cancer in the US with cancer has a much higher survival rate than the average person in the UK. Poor people may not have official insurance but that does not imply lack of healthcare in practice.